First and foremost, I must thank George Jansen, who literally spent months turning my first horrendous, stream of consciousness prose into a form suitable for publication. He is truly the unsung hero of this work, and an editor extraordinaire.
Jon Forrest and Evi Nemeth both beat the tutorial chapters to death. Their feedback was extremely valuable in helping to trim and focus those chapters into a more useful form. Never let it be said that too many cooks spoil the broth - in this case they helped flavor it toward perfection.
Cricket Liu kindly reviewed the DNS chapter, where he found a few errors that somehow slipped by all the others. Bruce Mah and Sean Brennan were guinea pigs for the first and second editions respectively. They set up and ran sendmail based on early drafts and thereby uncovered omissions and mistakes that required correction. Gavin Cameron bravely applied the checkcompat() examples to real-world situations, thereby helping to debug that code for me. And John Funk kindly allowed alpha versions of sendmail to run in production mode at Mercury Mail.
Needless to say, this book would not have been possible at all if Eric Allman had not written sendmail in the first place. Every draft has passed through his hands, and he has spent many hours ensuring technical correctness, providing valuable insight, and suggesting interesting solutions to sendmail problems.
Neil Rickert, too, saw every draft of the 1st edition. But, alas, circumstances beyond his control forced him to bow out from the 2nd edition.
For this 2nd edition, Cricket Liu kindly reviewed Chapter 21, and found several errors that slipped by everyone else.
Thanks and praise must go to Tim O'Reilly for agreeing to do this book in the first place. His experience has shaped this book into the form it has today. He was aware of the "big picture" throughout and kept his fingers on the pulse of the reader. Without his advice, a book this complex and massive would have been impossible.
Additional thanks must go to Lenny Muellner for tuning troff macros to satisfy the needs of this somewhat unique manuscript, and to Edie Freedman for gracefully accepting my unhappiness with so many cover designs except the current one, which I consider perfect.
The production folks at O'Reilly & Associates did a yeoman's job of achieving an outstanding finished book. So a special thank you to John Files for managing the project, Barbara Willette for copy editing, Nancy Kotary for help with final production, Kismet McDonough-Chan for her help in each phase of the production, Chris Reilley for the figures, Mary Anne Weeks Mayo for helping with quality control, Curt Degenhart, Madeleine Newell, and Ellie Fountain Maden for making the edits, Seth Maislin for doing the index, and Danny Marcus for proofreading.
Finally, thanks to a list of folks, each of whom helped in small but notable ways: Keith Johnson; Paul Pomes; Frederick Avolio; John Halleck; John Beck; Brad Knowles; Andrew Chang; Shau-Ping Lo; Nelson Morgan; Julene and Jake Bair; William Carter; all the folks at the International Computer Science Institute; John Funk, Dan Casson, and others at Mercury Mail; to many of those who sent interesting questions to the firstname.lastname@example.org mailing list; and to all the postings to the comp.mail.sendmail news group.